A wide variety of polyphenols known as secondary metabolites of plants are present in the plant kingdom. Some of these polyphenols have been found to show diversified physiological activities. It has heretofore been disclosed that catechin contained in tea has physiological activities such as antibacterial activity, antioxidative activity, anticancerous activity, antiallergic activity, deodoring activity, antiviral activity and blood cholesterol oxidation inhibiting activity (See JP-A-63-214183, JP-A-2-6499, JP-A-4-178320, etc.).
Further, in JP-A-7-285876, it is reported that polyphenols contained in extracts of unripe apples, unripe pears or unripe peaches have activities such as antioxidative activity, blood pressure reducing activity, antimutagenic activity, antiallergic activity, anticariogenic activity and deodoring activity. In addition, in “Japanese and Chinese Medicine—New Edition” (author: Kaneyoshi Akamatsu, Ishiyaku Syuppan Kabushiki Kaisha, published in 1980, pp. 359 to 360, J. Liquid Chromatography, 15(4), 637 to 646(1992)), it is mentioned that apples contain tannins. However, all the mention is for apples to be eaten fresh or apples to be processed, and no mention is made of crab apples.
Thus, it has been found that tea and unripe fruits, for example, have diversified physiological activities. The present inventor has made intensive studies on a process for producing a polyphenol having a wide variety of physiological activities economically and efficiently and on raw materials. As a result, the inventor has found that crab apples contain a significantly large amount of polyphenols, particularly a condensation tannin (procyanidin). The present invention has been completed based on this finding.